Ethernet devices can operate according to the IEEE 802.3 standard, and more specifically to communications that comply with the IEEE 802.3 clause 22, a clause 22 extensions, or clause 45 formats. Some registers of an Ethernet device are published mandatorily, others can optionally be published depending on product feature support, and other registers can be “Vendor Specific”, which can be used to customize proprietary functions. These registers can also be accessible by a management entity (e.g. a Host PC or processing controller also called Station Management (STA) in the IEEE 802.3 standard) using a Management Data Input/Output (MDIO) protocol and a MDIO controller implemented in hardware on an Ethernet physical layer Integrated Circuit, for example.
Some register fields can also support behavior defined by the IEEE standard. For example, a “Clear on Read” is an operation field indicating to clear to zero after a read from the STA. In another example, a “Reserved” field can indicate that a write from STA has no effect, where a read is always zero.
With possible standard evolution, or change of a feature-set, there is a need to update register field definition, behavior, or add registers to be published based on the MDIO or MMD device. Beforehand, MDIO-Management device (MMD) definition updates only utilized a hardware re-spin or re-fabrication because of, for example, the tight coupling of registers with the MDIO controller implemented in hardware. The execution of a behavior associated with a field is also usually utilized to generate an interrupt to a microcontroller to implement the field clearing after read or masking a write to a reserved field.